Experimental testing and theoretical characterization of an oil gelation process under shearing

Abstract

This work uses the Scanning Brookfield Test (SBT) in order to carry out an experimental testing of an oil gelation process under shearing. This test measures viscosity continuously at constant shear rate of 2 s−1 as the oil is cooled at a constant rate of 1°C per hour from −5 to −45°C. Apart from this standard way of running we changed the measuring conditions (basically by cooling the oil at quiescent temperature up to a desirable temperature), which permitted us to evaluate the real influence of a soft shearing on the rheology of a lubricant oil. We observed the slowing down of the gelation process of a lubricant oil subjected to shearing, which was explained due to the alignment of the crystal platelets in the way of the shear and the subsequent slowing down of the probability of collision. The use of a mathematical approach that uses the homogeneous nucleation theory and it takes into account the Bachelor equation permitted us to find a mathematical expression that provides the relative viscosity of the oil versus the temperature. This explains the slowing down of the gelation process caused by the shearing of the lubricant oil.